In general, a movement path of a tool and revolutions per minute of the tool are numerically controlled, and as a result, a machine tool performs a cutting process of a work. Examples of a machine tool include a machining center, a turning center, an NC milling machine, and the like. The machine tool is also referred to as a numerically controlled composite machine.
The tool includes a rotating cutting tool that performs a cutting process on a workpiece which is rotated and stopped while being mounted on a spindle. Examples of the rotating cutting tool include an end mil, a milling tool, a drilling tool, a boring tool, and the like. Hereinafter, the “rotating cutting tool” is abbreviated as the “tool”.
It is evaluated that productivity of the machine tool is good as material removal rate (MRR) per time is higher and it is evaluated that a processing grade is good as surface roughness of a processing surface is smooth.
A cutting volume per time is determined according to cutting condition elements such as a radial cutting depth, an axial cutting depth, main axis revolutions per minute, and a movement speed. If any one of the cutting condition elements is increased, the cutting volume is increased.
Meanwhile, there is a case that a cutting condition of the tool is presented as a manual recommendation condition by a tool manufacturer. However, the manual recommendation condition is provided based on a maximum allowable static processing load and is a value in which a chatter vibration characteristic which occurs during the cutting process is not reflected.
Accordingly, there is a problem in that it is impossible to handle breakage of the tool or the workpiece under chatter vibration which occurs during the cutting process and a dynamic processing load amplified through the chatter vibration. As a result, a worker tends to perform the cutting process by setting a much more stable cutting condition than the manual recommendation condition.
The processing condition includes a tool type, a tool shape, a tool protruding length, the number of tool blades, hardness of the work, processing point positions (X, Y, and Z coordinate positions) in a factory machine, and the like and the chatter vibration has a characteristic that the chatter vibration is continuously varied according to the processing condition.
That is, the worker applies a very conservative cutting condition among the manual recommendation conditions presented by the tool manufacture in order to ensure a processing quality, and as a result, the productivity deteriorates.
Accordingly, vibration suppression and vibration avoidance through evaluation and analysis of a vibration characteristic are continuously required when the cutting process is in progress in order to satisfy both productivity improvement and the processing grade.